Gas bulb for a gas-filled dial thermometer

ABSTRACT

A gas bulb for a gas-filled thermometer, the bulb containing activated coconut charcoal, and having dimensions such that the internal volume is about 0.15 cubic inches, operating on the principal of adsorption and emission of an agent of the activated coconut charcoal, thus indicating an appropriate change in temperature depending upon the amount of agent emitted or absorbed by the activated coconut charcoal.

United States Patent [1 1 Tortoso Oct. 23, 1973 GAS BULB FOR AGAS-FILLED DIAL 3,410,141 11/1968 Zurstadt 73/3682 THERMOMETER 2,475,3177/1949 Gess 73/3686 X [76] Inventor: John Tortoso, 405 Beach 9th St.,

Far Rockaway, NY. 11691 [22] Filed: Apr. 21, 1971 [21] Appl. No.:135,959

[52] US. Cl. 73/3682, 73/3686 [51] Int. Cl. G011: 5/36 [58] Field ofSearch... 73/3682, 368.6; 53/22 [56] References Cited UNITED STATESPATENTS 2,426,663 9/1947 Bevins 73/3682 BOURDON I TUBE PrimaryExaminer-Richard C. Queisser Assistant Examiner-Daniel M. YasichAttorney-Sughrue, Rothwell, Mion, Zinn & Macpeak [57] ABSTRACT A gasbulb for a gas-filled thermometer, the bulb containing activated coconutcharcoal, and having dimensions such that the internal volume is about0.15 cubic inches, operating on the principal of adsorption and 7emission of an agent of the activated coconut charcoal, thus indicatingan appropriate change in temperature depending upon the amount of agentemitted or absorbed by the activated coconut charcoal.

13 Claims, 2 Drawing Figures FIG] BOURDON TUBE PAIENIEhm 2a m mmcen zeoINVENTOR JOHN TORTOSO BY -3 M,Mwdl, M, I i Mc QK momma FIG. 2

BULB TEMPERATURE F GAS BULB FOR A GAS-FILLED DIAL THERMOMETER BACKGROUNDOF THE INVENTION 1. Field of the Invention The present invention relatesto a novel gas bulb to be used in gas-filled thermometers.

2. Description of the Prior Art There are two basic systems in standardgas bulb thermometer operation. One uses gas only and the other uses gasand gas-adsorbing material in the gas chamber (i.e., in the gas bulb).

The one which uses gas only depends on pressure generated by volumetricchange, which in turn is caused by temperature excursions inposed on thegas. It can be shown from physical laws then, that the size of the gasbulb used must vary inversely with the temperature range.

The one that uses an adsorbent material in the gas chamber depends onpressure generated by volumetric change due to temperature excursionsimposed on the gas, plus pressure caused by the adsorption/emission ofthe gas in the adsorbent material. Prior-art thermometers of this type,however, have made no apparent attempt to control the ratio of pressuredue to thermal expansion versus pressure due to adsorption/emission fromthe adsorbent material. As a consequence, bulb size must vary inverselywith the temperature range with this type also.

Ordinarily, prior art thermometers of the gas-only type are suitable fortemperature ranges of from 40 to 800F. The variety with adsorbentmaterial in the gas bulb are suitable for temperature ranges of fromwell below -40 to about 550F.

The gas bulb size of the gas-only variety typically varies from 0.5 to 1inch in diameter and from 3.5 to 14.75 inches in length; while that ofthe type employing adsorbent material generally varies upward from 0.33inch in length and 3 inches in diameter.

For example, the Taylor Instrument Co. manufactures a gas -only type(Catalogue No. 21P40l) with a gas bulb having a volume of about 52cc anddimensions of 0.5 inch in diameter and a length of 14.75 inches.

Typically, the standard gas bulb is connected to a Bourdon gauge whichregisters a change in temperature by the amount of expansion orcontraction of the Bourdon element depending upon the change of volumeof the material in the gas bulb. The conventional gas bulb of the gasonly variety might typically contain carbon dioxide, nitrogen, argon orany other similar gas; The pressure changes which operate the Bourdongauge are those which may be read from the pressure/- temperature curveof the gas being used, the. Bourdon gauge reacting linearly withpressure change.

For example, U.S. Pat. No. 3,410,141 to Zurstadt discloses a gas chargedremote thermometer having a thermal bulb charged withan expansible gasand a gasadsorbent material (e.g., charcoal) which adsorbs gas moleculesonto its surface at low temperatures and re leases the molecules athigher temperatures. As a result, the increased pressure in the systemresults in an unwinding movement of the Bourdon tube gauge with aconsequent movement of the indicator on the gauge, thereby registeringthe change in temperature. The movement of the indicator on the Bourdongauge is proportional to the temperature change in the indicating gasbulb. The gas bulb is connected to the Bourdon gauge through a capillarytube, enabling the increase in pressure in the gas bulb to betransmitted to the Bourdon gauge. Zurstadt discloses that the volume ofthe gas bulb is substantially greater than the total volume of thecapillary tube and the Bourdon tube, and as an example, discloses a bulbhaving; a volume of about 0.27 cubic inch (i.e., a diameter of about0.33 inch and a length of about three inches).

U.S. Pat. No. 2,426,663 to Bevins discloses a temperature responsivesystem comprising a compensating Bourdon tube connected with a gasadsorption medium having adsorbing and diffusing qualities responsive totemperature changes, the gas adsorption medium being a material such asactivated coconut charcoal granules. The gas bulb is completely filledwith the activated coconut charcoal and then evacuated at a temperatureof about 150C. and then charged with a suitable dry gas such as carbondioxide. The bulb is then sealed and connected to the Bourdon tube foroperation.

Some of the prior art devices require different size gas bulbs andcapillary tubes for sensitivity to certain temperature ranges. Forexample, the following table shows the relationships that exist forprior art devices between gas bulb size, length of connecting capillarytube and temperature sensitivity:

Bulb Size (length x diameter) Maximum Length Temperature (inches) ofCapillary (feet) Sensitivity (F) 5 X 25 40 to 180 10 X it 40 to 180 5.5X A 50 20 to 240 15 X Y4 Accordingly, with present techniques, it issometimes necessary to change bulb size to extend the temperaturesensitive range of the thermometer; in view of the limited range oftemperature for a given gas bulb size.

The basic reason for a change in gas bulb size to accomodate temperaturerange changes is because prior art thermometers are primarilygas-expansion dependent. It can be seen from thevolume/temperature/pressure relationships of any common gas that it isimpractical to construct a system with useable operating pressures atthe high end of the temperature range and sufficient pressure to operatethe same system 'at the low end of the temperature range. Thealternative, therefore, is to adapt the gas volume (bulb size) to rangeswhich encompass practical pressure excursions.

Accordingly, it would be desirable to provide a gasfilled thermometerutilizing a gas bulb of one size which would be applicable to a widerange: of temperature and also which would be accurate over the entireapplicable temperature range.

' It is a primary object of the present invention to provide a gas bulbfor a gas-filled thermometer which rem-. edies the disadvantages of theprior art gas bulbs.

It is another object of the present invention to provide a gas bulb fora'gas-filled thermometer which utilizes one size gas bulb for a verywide temperature range.

It is yet another object of the present invention to provide a gas bulbfor a gas-filled thermometer wherein the one size gas bulb is extremelyaccurate over a ver wide temperature range.

It is still another object of the present invention to provide a gasbulb for a gas-filled thermometer wherein the bulb is very small in sizeand yet sufficient to provide very accurate readings over a widetemperature range.

Other objects and advantages of the present invention will becomeapparent from the ensuing description.

SUMMARY OF THE INVENTION The present invention provides a cylindricalgas bulb for a gas-filled thermometer having a volume of about 015 cubicinch, and containing therein a small amount of activated coconutcharcoal as the adsorbent material. Preferably, the coconut charcoal hasa size of from 6 to 15 mesh, the amount of coconut charcoal containedwithin the gas bulb being from about 0.6 to about 0.8 gram. The gas bulbof the present invention is extremely accurate over a temperature rangeof from -40to 500F.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view ofthe gas bulb of the present invention; and

FIG. 2 represents the pressure temperature relationships that exist in aprior art thermometer and in the device of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings,the gas bulb of the present invention is shown in cross-section inFIG. 1. The gas bulb is generally designated 1 in FIG. 1 and comprises acylindrical casing 2 defining a chamber therein, portion 8 of thechamber'being separated from portion 7 of the chamber by means of afilter 3. Disposed within portion 8 of the chamber are a plurality ofactivated coconut charcoal particles4 and extending into chamber portion7 is a capillary tube 5, supported by means of member 6. Capillary tubeis connected at the other end (not shown) to the temperature gauge inthe indicator portion of the thermometer.

As shown in FIG. 1, portion 8 of the chamber has a certain length L- anda certain diameter D. For the purposes of the present invention, thepreferred length of chamber portion 8 is about 1,375 inches while thepreferred diameter of chamber portion 8 is about 0.250 inch. Actually,these dimensions may be varied as desired so long as the internal volumeof the gas bulb is about 0.15 cubic inch. Thus, the diameter may varyfrom 0.250 to 0.375 inch and the length from 1.350 to 1.5 inch.

As described above, the gas and adsorbent material type thermometerrelies on the pressure generated by the expanding gas plus the increasein pressure due to the gas emitted from the adsorbent material. However,

prior art thermometers of this type exhibit a very strong dependency onthe gas .volume in the gas bulb, whereas the gas bulb of the presentinvention reduces and substantially eliminates this dependency.

Further, the ratio of the dependency of pressure due to expansion of gasversus emitted gas in prior art thermometers is unpredictable, as can beseen by referring to FIG. 2.

Curve A is a curve showing prior-art temperature versus pressure. TheZurstadt patent describes'an eight to 10 times increase in the slope ofthe curve when compared to a standard gas filled bulb. Curve Bdemonstrates a truly adsorption-emission system with an increase overthe slope of the standard gas bulb equal to or better than the priorart. The significant difference is in the pressure increase, with adecrease in bulb size, linearly over a normal range.

Prior-art adsorbent-emission thermometers are sensitive to the volume ofthe capillary leading to the indicator, showing a dependency on the gasin the sensing bulb. By comparison, the gas bulb of the presentinvention is not sensitive to the length and size of the capillary, upto about feet. This indicates a relative lack of dependency on the gasvolume in the sensing bulb, and thus a primary dependency on theadsorption/emission of the gas.

This feature enables the gas bulb of the present invention to provideextremely accurate and easily reproducible temperature measurement dueto the lack of dependency on the gas volume in the gas bulb.

The use of the gas bulb of the present invention having the dimensionabove described provides for an extremely accurate temperaturemeasurement over a wide range of temperature, i.e., from about 40 to500F. The accuracy of the gas-filled thermometer using the gas bulb ofthe present invention is such that the error factor is less than 2percent over the entire range of temperature given above.

Ordinarily, tha material which is contained within chamber portion 8,constitiuing the adsorbing and gasreleasing material, is coconutcharcoal which has been activated by certain procedures; since activatedcoconut charcoal is very advantageous from the viewpoint of reliabilityand repeatability.

For the best results, it is preferred to incorporate into chamberportion 8 from 0.6 to 0.8 gram of the activated coconut charcoal.Preferably, about 0.6 gram of the activated coconut charcoal iscontained within chamber portion 8 of the gas bulb of the presentinvention.

In order to achieve the best results, the procedure which is followedfor activating the coconut charcoal in the gas bulb is very important.In other words, if the proper procedure is followed, an excellentaccuracy over the temperature-sensitive range is assured and theoperation of temperature sensing is extremely predictable andrepeatable.

The preferred procedure for adding and activating the coconut charcoalto the gas bulb of the present invention will be described hereinbelow.Firstly, about 0.6 gram of coconut charcoal having a size of about 6 ito about 15 mesh is placed into the gas bulb of the present inventionand a screen filter 3 is placed over the end of chamber portion 8 of thegas bulb. A capillary tube is then inserted into chamber portion 7. Thebore of the capillary is preferably about 0.007 inch, but a capillaryhaving a bore of from 0.007 to 0.010 inch may be employed.

The gas bulb is then attached to a suitable indicating means (e.g., aC-shaped Bourdon tube), and the resulting system is then evacuated(20-30 inches of mercury) for a period of time of from 4 to 6 hours inorder to remove any foreign gas from the closed system. While under thevacuum conditions, the gas bulb is heated several times in order todegas the charcoal. During this heating, the temperature should beapproximately 900F., although a temperature ranging from 800 to 900F. issatisfactory.

After the last time the gas bulb is heated to the aforedescribedtemperature, it is placed in a bath at a temperature approximately 10Fabove the bottom of the range which the thermometer is designed to read,and the system is then pressurized to a pressure of from 100 to 180 psiif a C-shaped Bourdon is used, or to about 360 psi with a spiral-shapedBourdon, with a gas such as nitrogen, or any other conventional inertgas used in prior art thermometers of this type.

The system is then sealed off and the thermometer is now ready tofunction. However, one further modification of the speed control isnecessary because coconut charcoal does not emit a gas linearly. Aspecial lug is used to compensate for the inaccuracy that occurs duringfilling of the gas bulb.

In addition to the particular dimensions of the gas bulb of the presentinvention, the mesh of the activated coconut charcoal is an importantfactor in obtaining accurate temperature readings. A very large or verysmall mesh is undesirable because the surface area of the charcoal wouldbe reduced, thus reducing the ratio of gas adsorbent and emitted, whichwould not provide a sufficiently large force to drive the indicatingmeans. The most preferred size for the activated coconut charcoal forthe purposes of the present invention is from 6 to 15 mesh.

Any arrangement of a pressure-sensitive temperature indicator and thegas bulb described above which will result in an indication of theproper temperature according to the pressure changes in the gas bulb issatisfactory for purposes of the present invention. It is to beunderstood that the particular indicator device employed in conjunctionwith the gas bulb is not critical to the present invention, but rather,it is the gas bulb per se and the method of charging the same whichconstitutes the most important aspects of the present invention; thatis, with respect to the gas bulb per se, the most important feature isthe size thereof in relation to the designated temperature sensitiverange. In other words, any conventional means may be employed which issensitive to the pressure change in the gas bulb and which willaccurately convert such pressure change to a temperature change.

Although the length of the capillary tube from the gas bulb to theindicator device is not critical, it is generally preferred that thelength of the capillary be from 10 feet to 100 feet.

What is claimed is:

1. A gas bulb for a gas-filled remote thermometer consisting essentiallyof a cylindrical inert gascontaining housing having an internal volumeof no greater than 0.15 cubic inch, said housing also containing agas-adsorbing material degassed of substantially all foreign gases andwhich adsorbs and emits said inert gas with a proportional change intemperature, said gas-adsorbing material consisting essentially only ofactivated coconut charcoal having a size of from about 6 to mesh andbeing present in an amount of from 0.6 to 0.8 gram, said gas bulbproviding accurate and measurable changes of pressure within saidhousing due to the adsorption and emission of said gas by saidgasadsorption material over the entire temperature range of from -40 to500F.

2. The gas bulb of claim 1 wherein said housing has a diameter offromabout 0.250 to about 0.375 inch and a length of from about 1.350 toabout 1.5 inch.

3. The gas bulb of claim 2 wherein about 0.6 gram of said activatedcoconut charcoal is: present in said hous mg.

4. A remote thermometer system effective over a temperature range offrom -40 to 500F. comprising the gas bulb of claim 1, apressure-sensitive temperature indicator and a capillary tube connectingsaid glass bulb and said indicator, whereby said indicator registers thetemperature which said gas bulb is subjected to by means of the pressurechange in said gas bulb communicated to said indicator through saidcapillary tube, said gas bulb having been pressurized with said inertgas at a temperature of about -30F.

5. The remote thermometer system of claim 4 wherein said gas bulb ispressurized to a pressure of from to 360 psi.

6. The thermometer system of claim 4 wherein said indicator is a Bourdontube temperature gauge.

7. The thermometer system of claim 6 wherein the length of saidcapillary tube varies from 10 to 100 feet and wherein tl' e bore of saidcapillary tube varies from (i007 to 0.010 inch.

8. The thermometer system of claim 7 wherein the bore of said capillarytube is about 0.007 inch.

9. The gas bulb of claim 1 wherein said housing contains said inert gasin an amount sufficient to provide a pressure of from 100 to 360 psi,said gas bulb having been pressurized at a temperature of about 10Fhigher than the lower temperature of the range of temperature said gasbulb is adapted to measure.

10. A method of charging a gas-filled remote thermometer designed tooperate accurately over a given temperature range with a gas-adsorbingmaterial comprising;

1. providing a gas bulb having an internal volume of no greater than0.15 cubic inch;

2. charging said gas bulb with from 0.6 to 0.8 gram of a gas-adsorbingmaterial consisting essentially only of activated coconut charcoalhaving a size of from 6 to 15 mesh;

3. providing a pressure-sensitive temperature indicating deviceandconnecting said device to said gas bulb by means of a capillary to forma remote thermometer system;

4. simultaneously evacuating said thermometer system and heating saidsystem to substantially completely degas said gas-adsorbing material;

5. heating said system to a temperature of about 10F. above thelowertemperature of said given range; and

6. pressurizing said system with an inert gas.

11. The method of claim 10 wherein said system is evacuated to apressure ,of from about 20 to about 30 inches of mercury andsimultaneously heated several times to a temperature of from 800 to 900Fover a period of from 4 to 6 hours.

12. The method of claim 11 wherein said system is pressurized to apressure of from 100 to 360 psi with nitrogen, carbon dioxide or argon.

13. The method of claim 12 wherein said given temperature range is from40 to 500F.

1. A gas bulb for a gas-filled remote thermometer consisting essentiallyof a cylindrical inert gas-containing housing having an internal volumeof no greater than 0.15 cubic inch, said housing also containing agas-adsorbing material degassed of substantially all foreign gases andwhich adsorbs and emits said inert gas with a proportional change intemperature, said gasadsorbing material consisting essentially only ofactivated coconut charcoal having a size of from about 6 to 15 mesh andbeing present in an amount of from 0.6 to 0.8 gram, said gas bulbproviding accurate and measurable changes of pressure within saidhousing due to the adsorption and emission of said gas by saidgas-adsorption material over the entire temperature range of from -40*to 500*F.
 2. The gas bulb of claim 1 wherein said housing has a diameterof from about 0.250 to about 0.375 inch and a length of from about 1.350to about 1.5 inch.
 2. charging said gas bulb with from 0.6 to 0.8 gramof a gas-adsorbing material consisting essentially only of activatedcoconut charcoal having a size of from 6 to 15 mesh;
 3. providing apressure-sensitive temperature indicating device and connecting saiddevice to said gas bulb by means of a capillary to form a remotethermometer system;
 3. The gas bulb of claim 2 wherein about 0.6 gram ofsaid activated coconut charcoal is present in said housing.
 4. A remotethermometer system effective over a temperature range of from -40* to500*F. comprising the gas bulb of claim 1, a pressure-sensitivetemperature indicator and a capillary tube connecting said glass bulband said indicator, whereby said indicator registers the temperaturewhich said gas bulb is subjected to by means of the pressure change insaid gas bulb communicated to said indicator through said capillarytube, said gas bulb having been pressurized with said inert gas at atemperature of about -30*F.
 4. simultanEously evacuating saidthermometer system and heating said system to substantially completelydegas said gas-adsorbing material;
 5. heating said system to atemperature of about 10*F. above the lower temperature of said givenrange; and
 5. The remote thermometer system of claim 4 wherein said gasbulb is pressurized to a pressure of from 100 to 360 psi.
 6. Thethermometer system of claim 4 wherein said indicator is a Bourdon tubetemperature gauge.
 6. pressurizing said system with an inert gas.
 7. Thethermometer system of claim 6 wherein the length of said capillary tubevaries from 10 to 100 feet and wherein the bore of said capillary tubevaries from 0.007 to 0.010 inch.
 8. The thermometer system of claim 7wherein the bore of said capillary tube is about 0.007 inch.
 9. The gasbulb of claim 1 wherein said housing contains said inert gas in anamount sufficient to provide a pressure of from 100 to 360 psi, said gasbulb having been pressurized at a temperature of about 10*F higher thanthe lower temperature of the range of temperature said gas bulb isadapted to measure.
 10. A method of charging a gas-filled remotethermometer designed to operate accurately over a given temperaturerange with a gas-adsorbing material comprising;
 11. The method of claim10 wherein said system is evacuated to a pressure of from about 20 toabout 30 inches of mercury and simultaneously heated several times to atemperature of from 800* to 900*F over a period of from 4 to 6 hours.12. The method of claim 11 wherein said system is pressurized to apressure of from 100 to 360 psi with nitrogen, carbon dioxide or argon.13. The method of claim 12 wherein said given temperature range is from-40* to 500*F.